NONOate

 ( Nitrosyl Compounds ) 

In chemistry, a NONOate, also called a diazeniumdiolate,

is a compound having the chemical formula R¹R²N−(NO⁻)−N=O, where R¹ and R² are alkyl groups. These compounds are unusual in having three sequential nitrogen atoms: an amine functional group, a bridging NO⁻ group, and a terminal nitrosyl group. Almost all known examples form with the oxygen atoms cis to the double bond, which is also the more thermodynamically stable configuration.

NONOates form reversibly when a pure secondary amine is exposed to nitric oxide:2R2NH + 2NO <=> R2NH2+R2N(NO)2-

In contact with water, these compounds release NO (nitric oxide).

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pH-dependent decomposition of NONOates

Most NONOates are stable in alkaline solution above pH 8.0 (e. g. 10 mM sodium hydroxide) and can be stored at −20 °C in this way for the short term. To generate NO from NONOates, the pH is lowered accordingly. Typically, a dilution of the stock NONOate solution is made in a phosphate buffer (pH 7.4; Tris can also be used) and incubated at room temperature for the desired time to allow NO to accumulate in solution. This is often visible as bubbles at high NONOate . Incubation time is important, since the different NONOates have different half-lives ( t_1/2) in phosphate buffer at pH 7.4. For example, the half-life of MAHMA NONOate under these conditions is ~3.5 minutes, whilst the t_1/2 of DPTA NONOate is 300 minutes. This is often useful in biological systems, where a combination of different NONOates can be used to give a sustained release of nitric oxide. At pH 5.0, most NONOates are considered to decompose almost instantaneously.

Categories: Nitrosyl Compounds, Functional Groups

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